'backscratcher' originates from English, specifically as a compound of 'back' and 'scratcher' (the agent noun formed from 'scratch').

'back' comes from Old English 'bæc' meaning 'the back of the body', and 'scratch' developed in Middle English from earlier Germanic forms; the agent suffix '-er' produced 'scratcher', and the compound 'backscratcher' formed in modern English to name the tool.

Initially a transparent compound naming its function ('a device for scratching the back'); the basic meaning has remained stable as the name of that tool.